Man, I know how you feel...when I was doing Vegas and AC, it never failed, we always had some Wise Guys come in to see the show and pull out the giant stoggies and just continue to puff away not thinking about anyone but them selves....I think that Al has the solution, open a window on one side of the room and put a big fan onthe other side of the room facing out the other open window.....I think the sign would only prove
to make some of them somke more if you know what I mean....Try wearing an oxygen mask between songs and when they ask why the mask you can tell them it's because of the smoke
maybe it will make them wake up....good luck